Throughout history there have been many military doctrines that have withstood the test of time; the 2010 Strategic Defence and Security Review is not one of them.

A few more pages of that maligned document will be torn out and tossed away with the announcement by the defence secretary, Philip Hammond, about the restructuring of the army.

It is worth remembering the SDSR and the accompanying National Security Strategy envisaged a slightly smaller force – reduced from just over 100,000 to 94,000.

Hammond will confirm how the army will cut to an overall size of 82,000, by the scrapping and merging of battalions.

It has taken the best part of two years for the government to get to this point – two years in which military budgets have been constantly revised and assumptions in the SDSR challenged, as the need for extra job cuts became all too apparent.

Written in haste because the Treasury would not tell the Ministry of Defence how much money it had to spend, the SDSR was a self-inflicted wound reopened on countless occasions since it was published.

That has caused great bitterness and prolonged anxiety within the MoD's Main Building, in regiments throughout the country, and among personnel serving in Afghanistan.

Gone with the men and women from the units axed on Thursday will be any pretence that the British armed forces will retain the global reach it had before the budget cuts.

The prime minister has doggedly stuck to the claim that Britain's global role will not be affected, but that does not stand up to scrutiny.

The SDRS envisaged the sharp end of the army to be built around five multi-role brigades, plus the Royal Marine Commandos and 16 Air Assault Brigade.

In the new structure there will be two fewer brigades. That means the military could not conduct simultaneous operations in Iraq and Afghanistan.

The head of the army, General Sir Peter Wall, hints as much in an editorial in Thursday's Times newspaper. He said it would be more important than ever to "form coalitions that include regional partners as well as our traditional allies. They are becoming ever more important both in political and military terms."

Roughly translated, it means we can't do this on our own any more. One of Wall's predecessors, General Sir Richard Dannatt, was starker. He said it was obvious the army would be constrained. "By definition, it will be able to do less," he told the BBC. "It's pretty obvious that if you are going to lose 20,000 troops you will lose important units."

Dannatt also said he expected up to 11,000 people might have to be made compulsorily redundant.

Those who favour the military cuts will be heartened by the downsizing, and may wonder why it hasn't gone further.

The rise of cyber capabilities in the military sphere and the use of unmanned drones, suggests future conflicts may be more automated and potentially less bloody.

But the next generation of warfare is still some way off and in the meantime, Dannatt warns the UK could get caught out. "Let's hope the next decade is less busy than the last decade. But I wouldn't bet on it."